HARRISBURG, Pa. — Pennsylvania’s highest court on Wednesday said people whose mail ballots are rejected for not following technical procedures in state law can cast provisional ballots, a decision sure to affect some of the thousands of mail-in votes likely to be rejected this fall.

The Supreme Court ruled 4-3 that Butler County’s Republican-majority election board must count provisional ballots that were cast by two voters after they learned their mail-in ballots were voided because they arrived without mandatory secrecy envelopes.

The decision was a legal defeat for the Republican National Committee and the state Republican Party, which had argued Butler County had correctly rejected the provisional ballots cast during the April primary.

Secrecy envelopes keep ballots concealed as elections workers open the stamped outer envelopes used to mail the whole packets back. Voters also must sign and date the exterior envelopes. Pennsylvania voters have so far applied for more than 1.9 million mail ballots.