SAO PAULO/BRASILIA (Reuters) - Brazil’s Supreme Court on Thursday ruled to restrict federal lawmakers’ protection from prosecution, a move hailed by some experts as a blow to impunity for the powerful, but a decision that may open new avenues for politicians to stall cases.

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Before the ruling, Brazil’s 594 members of Congress, roughly half of whom face some type of charge, could only be tried by the Supreme Court, whether or not their alleged crime took place before they were in the legislature.

Now, federal lawmakers will be tried by the high court for crimes allegedly committed while they were serving as federal congressmen and that are directly linked to their official roles.

That means the bulk of cases related to investigations that have uncovered stunning levels of political graft in Brazil must still be judged by the Supreme Court, which takes several years to decide cases because of a backlog of decisions.

That delay has allowed the overwhelming majority of lawmakers to avoid facing charges, granting de facto immunity for politicians who have constructed some of the most elaborate graft schemes the world has seen, prosecutors say.

Stripping away some of those protections is on balance a positive move, said Sergio Praça, a political scientist at the Getulio Vargas Foundation, a leading Brazilian university.

“It changes the strategy for corrupt politicians,” he said. “They always counted on the Supreme Court as a guarantee for impunity. It no longer is.”

However, there are concerns that the ruling, while in theory easing the case load for the high court, will make new loopholes that congressmen can use to skirt graft trials.

Supreme Court Justice Alexandre de Moraes said the ruling, for him, means that every accusation leveled against a member of Congress would still need to be heard by the high court, simply to determine if the politician’s case should be decided there or by a faster-moving lower court.

“Will we have to examine and break up each charge in every case?” he asked. “What will this mean for the investigations?”

In explaining his vote, Justice Jose Dias Toffoli agreed with Moraes, lamenting that the Supreme Court would “continue to weigh in, case by case” when lawmakers face charges.

Thursday’s ruling has no effect on Brazil’s executive branch, nor on the tens of thousands of other public servants who have some form of protection from prosecution by lower state and federal courts.