Secret Service details security plans for the Republican National Convention.

A Milwaukee park that is a few blocks from the arena hosting the Republican National Convention and has been at the center of a free speech lawsuit will be off limits to protesters during next month’s event, the Secret Service revealed, following intense lobbying by convention organizers.

Access to Pere Marquette Park will be limited to people with official credentials, a group that includes delegates and journalists, while the convention takes place in mid-July, officials with the Secret Service said at a news conference on Friday in Milwaukee.

Protesters had been eyeing the park, which is tucked between the Fiserv Forum, the convention arena, and the Milwaukee River, as a gathering place.

But Audrey Gibson-Cicchino, an assistant special agent and the Secret Service’s coordinator for the convention, said on Friday that its location next to the Milwaukee County Historical Society, which will host other official convention activities, presented a security risk.

“The executive steering committee determined that that location would need to fall within the security perimeter in order to ensure the highest level of safety for the convention,” she said.

The Secret Service designated two other parks outside of the inner security perimeter, an area roughly five blocks by seven blocks in the downtown, for protesters. The parks are farther from the arena, but inside the outermost security perimeter, where vehicles must pass through screening checkpoints.

The American Civil Liberties Union of Wisconsin, which sued the city this month on behalf of a protest umbrella group, criticized the size of the security perimeter and the inclusion of Pere Marquette Park within it.

“The expansion represents an impermissible concession to the Republican National Committee, which did not want to see or hear demonstrators near its convention,” Tim Muth, a staff attorney for the A.C.L.U. of Wisconsin, said in a statement.