DENVER – A federal judge on Tuesday blocked part of a 2016 voter-approved measure that makes it more difficult to amend the Colorado Constitution.

The ruling could have a big impact on various measures proposed or under discussion for the state’s November ballot.

U.S. District Judge William Martinez declared unconstitutional a part of Amendment 71, dubbed “Raise the Bar,” setting tougher standards for the circulation of petitions to put a constitution change on the statewide ballot.

The new rule said at least 2 percent of each petition’s signatures must be gathered in each of Colorado’s 35 state Senate districts.

That portion of Amendment 71 violates the U.S. Constitution’s principle of “one person, one vote,” because of the difference in the registered-voter population of the various Senate districts, the judge ruled.

Martinez had objected to the provision in a preliminary ruling last month, but gave state officials a chance to show justification for it on constitutional grounds.

Tuesday, he permanently enjoined officials from enforcing 71’s tougher signature-gathering rule, saying that unless the state “can reshape its state senate districts to embrace roughly equal total and registered voter population,” the rule violates the U.S. Constitution’s Equal Protection Clause.

Prior to 71’s passage, there was no rule about gathering a minimum number of signatures in each Senate district. Signatures could be collected without regard to geography.

That often meant that petition drives focused on Colorado’s heavily populated Front Range counties and skipped rural areas.

Martinez’s ruling left in place another part of Amendment 71, however – one that requires a 55-percent-majority vote in an election to approve constitutional changes, up from the simple majority previously required.

Once the constitution is altered by a public vote, the change can only be repealed by another public vote, not by the legislature.

Amendment 71 was backed by business groups and others who argued that the ease with which the Colorado Constitution could be permanently changed hampered the state’s economy by creating uncertainty and political expense for business. In particular, oil and gas groups that were worried about various efforts to regulate their activities pushed for the measure.

Roughly half of the $4.7 million raised to support passage of 71 came from an oil-and-gas-backed group.

But advocates for a variety of causes – including restrictions on gerrymandering, universal health care and a housing development slowdown – joined in suing to challenge “Raise the Bar.” The measure also was opposed by a spectrum of political groups, including the Independence Institute, the National Education Association, Conservation Colorado and the Bell Policy Center.

Plaintiffs’ attorney Ralph Ogden told The Associated Press that Amendment 71 at least tripled the cost of gathering signatures for Colorado constitutional amendments.

Colorado Secretary of State Wayne Williams signaled plans to appeal Tuesday’s ruling and to seek a stay of Martinez’s order that might keep 71’s provisions in place through November.

“More than 55 percent of Colorado voters approved Amendment 71 and we will support Colorado’s voters,” Williams said last month when Martinez issued his preliminary ruling. ” … Colorado’s voters clearly stated that there should be input from all of Colorado, not just a county or two, when amending our state constitution.”

Kate Roberts, who managed the Amendment 71 campaign, also vowed an appeal, saying Martinez used “tortured logic” in reaching his conclusion.

Whether 71 remains in effect or not, advocates of various causes have the option of following the easier process of placing statutory measures to change state laws on the ballot. Such measures still require only a simple-majority vote. But they also can be revised by the legislature.