India, Sept. 4 -- A federal judge in Boston will hear arguments Thursday on whether to extend her prohibition against the US Postal Service requiring states to use a new mail balloting system for the midterms as part of an executive order by President Donald Trump.

The hearing in the closely watched case comes the day before the first state begins sending mail ballots to voters. US District Court Judge Indira Talwani is considering whether to order a preliminary injunction that would bar the Postal Service from requiring the new system to be used for the midterms. Last week, she imposed a 14-day temporary restraining order to keep it from being used.

That order expires next week as more states begin sending out mail ballots. Talwani has...