A proposed law in Ukraine’s parliament could limit the country’s ability to hold any future nationwide referendum on possible entry into NATO or the European Union, an official said Thursday. Days earlier, Ukraine President Petro Poroshenko established a rough timeline for the country’s entrance into the alliance and identified a referendum as a necessary step in the process.

Representatives from the four parties that compose Ukraine’s parliament jointly submitted the draft law, which was a new version of legislation enacted in 2012, Russian news agency Tass reported. The proposal “considerably narrowed” the circumstances under which Ukraine could hold a nationwide referendum, said Volodymyr Pilipenko, Ukraine’s representative at the Council of Europe’s Venice Commission, which advises European nations on issues of constitutional law.

“The new edition of the draft law envisages [nationwide referenda for] amendments to the Constitution, changes of the country’s territory and cancellation of certain laws,” Pilipenko wrote on his Facebook account, according to Tass. Conversely, the law would not allow for nationwide referenda on “ratification of treaties on joining NATO or the EU,” he said.

Ukraine was at the forefront of Eastern European nations interested in strengthened ties or full membership within NATO, as a check against Russia’s military expansion in the region. Russia annexed the formerly Ukrainian territory of Crimea in March 2014 and has been accused of providing military support and weaponry to separatist rebels active in eastern Ukraine.

NATO requires potential members to meet a checklist of requirements before they can gain entry into the alliance. Applicants must meet a threshold of democratic government, enact civilian oversight over armed forces and demonstrate a commitment to peaceful diplomacy, according to a 1997 U.S. State Department memo.

Ukraine will need “at least six, seven years” to meet NATO’s requirements, Poroshenko told an Italian newspaper earlier this week. He reiterated that the country would hold a nationwide referendum to determine if the civilian population supported entry into NATO.