ACTA may be scarier than SOPA, Internet freedom advocates say, and outrage over the Anti-Counterfeiting Trade Agreement treaty is growing as it gains international prominence in the wake of the U.S. Congress shelving the Stop Online Piracy Act last week.

Both the ACTA treaty and the SOPA bill are ostensibly aimed at limiting counterfeiting and piracy, but opponents argue that they would have the adverse effects of limiting Internet freedom, quashing innovation and possibly even censoring the Internet.

Google, Wikipedia, Reddit and other websites staged a successful SOPA blackout on Jan. 18, bringing the web together in opposition to the bill, and causing the Congress to have to go back to the drawing board on an anti-piracy bill.

And now ACTA opponents, from the Electronic Frontier Foundation to the Anonymous hacktivist collective are colaescing in opposition to the treaty as well.

Despite these key similarities, the ACTA vs. SOPA debate usually ends up with opponents ruling that ACTA is scarier in terms of what its worldwide impacts would be. Here are five of these reasons why these opponents believe ACTA is the greater threat to the Internet as we know it:

1. Scope: The key reason why ACTA is scarier to many Internet freedom advocates is the fact that it is an international treaty. SOPA was a bill before the U.S. Congress, and though it would have had some worldwide implications as it was aimed at stopping web piracy at overseas sites like Sweden's Pirate Bay torrent site.

ACTA, meanwhile, would set up an international legal framework to deal with issues of counterfeiting, piracy and other crimes. Instead of dealing with individual nation's laws regarding these issues, if ACTA is passed, countries would be able to adjudicate these crimes in a new governing body that would exist outside of the purview of the United Nations and other international institutions.

This opens up the possibility for ACTA to be used to crack down on Internet activity worldwide by a coordinated authority that rests outside of any country. SOPA, meanwhile, would have been enforced by existing American agencies, and would have been subject to legal scrutiny and constitutional challenges within the U.S. judiciary system.

2. Transparency: The SOPA debate took place mostly outside of the public eye at first, but because it was taking place in the halls of the U.S. Congress, Internet freedom advocates were able to monitor the proceedings, view draft bills and related materials and monitor the proceedings.

But the ACTA treaty is being negotiated almost entirely behind closed doors. If it were not for the advent of WikiLeaks, which released documents revealing details of the negotiations and draft versions of the treaty, the world community would still have very little knowledge of what exactly the treaty might entail.

This opens up major concerns for people who would like to ensure that the treaty does not infringe on people's rights or limit internet freedom in ways that would be detrimental to the web's status as a place where information flows freely.

3. Ease of Approval: The SOPA bill was derailed because it required both houses of the U.S. Congress to pass it, and for President Barack Obama to sign it. Once approved, it would have been subject to challenge and could have been changed by future congresses.

ACTA, on the other hand, was already signed by the United States on Oct. 11, 2011, and Obama was not required to get the approval of any outside authority to do so: not the Congress, not the Supreme Court, and not the American public.

Now that it has been signed, the legislative and judicial branches of the U.S. government also have little ability to challenge or amend the treaty, and Americans would be subject to a whole new scheme of laws, restrictions and regulations that could have them facing fines or jail through a process that would likely exist entirely outside the scope of the American justice system.

4. Level of Support: Even before the efforts of opponents brought down the controversial legislation, SOPA had only 31 co-sponsors in Congress, meaning it was never a wildly-popular bill to begin with. Despite the loud cries that SOPA was threatening the Internet as we know it and that Congress was about to pass it, it was never really that close to being made into law.

ACTA, on the other had, is an international treaty, meaning that it requires unilateral signatures, not votes based at least in part on public opinion. And the Obama administration already signed the treaty for America on Oct. 11, 2011. Critics, including Democratic U.S. Senator, Sen. Ron Wyden of Oregon, have questioned the constitutionality of Obama being allowed to sign an international treaty of this sort without gaining approval from the U.S. Congress, but America remains a full signatory to this day.

And the United States is not alone in having signed on to ACTA: During the same Oct. 11 signing ceremony in Tokyo, Australia, Canada, Japan, Morocco, New Zealand, Singapore, and South Korea also signed the treaty, while the European Union, Mexico, and Switzerland have said they plan to do so in the near future. This means many of the world's largest nations not only support the treaty, they have gone so far as to have already signed it.

The G8 has also come out with a statement in support of the ACTA treaty, offering the following remarks on the topic in a July 2008 communique: We encourage the acceleration of negotiations to establish a new international legal framework, the Anti-Counterfeiting Trade Agreement (ACTA), and seek to complete the negotiation by the end of this year.

5. Visibility: The campaign to stop SOPA began relatively early on in its development. By the time it was even able to go to mark-up in the House Judiciary Committee, opponents were already loudly making their opinions known to a large slice of the Internet-using public.

ACTA, on the other hand, is largely off most people's radars, though it has been under official negotiation for about five years. Efforts against it in the United States are modest at best, and the U.S. has already signed the bill anyway. But they do persist, as a petition on with more than 6,000 signatures is currently on file with the Obama administration, calling on it to end ACTA and protect our right to Internet privacy.

But ACTA's visibility is rising in nations that have yet to sign the bill. Poland announced last week that it will sign the treaty on Jan. 26, drawing the ire of Polish groups opposed to the law, including representatives of the Anonymous collective. The opposition groups have threatened to stage a Web blackout that day similar to the SOPA blackout if the Polish government goes through with the signing. On Sunday the hacktivist collective shut down the Polish prime minister's Web site in order to demonstrate its opposition to ACTA, Poland's reported.

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