James Slater, the lawyer for Jack Sweeney, tells TMZ ... he and his partners don't see any realistic legal path for T-Swift and her attorneys to take if they wanna press this jet issue.

Now, Slater does say if there was any movement from Taylor's side -- namely, a lawsuit of some sort -- Sweeney's team would immediately respond with an anti-SLAPP motion ... a law that provides defendants a way to dismiss meritless lawsuits quickly.

JS adds to us the letter from Tay Tay's attorney, Kate Wright Morrone, had little legal substance, from his POV, and her assertation Jack committed stalking and harassing behavior by showing TS's flight path to the world was totally unfounded in the eyes of the law.

He basically blasts the whole thing as a big scare tactic ... asserting everything that needed to be addressed was written in the letter he sent to Swift's team -- and that nothing else really needs to be mentioned to make their point. Bottom line ... Sweeney ain't scared!

Quick recap ... things took off when TS' attorneys issued a legal threat to Sweeney in December, warning him that if he didn't stop putting their famous client's safety in imminent danger, he'd be subject to further legal action.

But Slater retaliated last month ... saying Taylor's camp cited no law supporting the cease and desist -- while also rebuffing the stalking claims ... saying it doesn't apply to his client whatsoever since Sweeney has never made a "credible threat" against Taylor through his words or actions.

He also pointed out the obvious ... Sweeney simply uploaded publicly available data from the Federal Aviation Administration to track Taylor's plane movements -- a point backed by aviation attorney Tim Loranger of Wisner Baum, who tells us this has been a longtime hobby for aviation buffs ... insisting there's no there-there to threaten a lawsuit or any legal action.

Loranger tells TMZ that whether aircraft owners like it or not ... their planes and jets have to be registered with the FAA and their registration numbers are displayed on their aircraft's side ...  making it pretty easy to be followed on flight tracking services.

We spoke to some more legal experts who weighed in on Swift vs. Sweeney -- and not everyone thinks he's in the clear. Civil attorney Tre Lovell of The Lovell Firm tells us that unless Sweeney can clearly describe the purpose for his actions ... he'd suggest Sweeney treads very carefully moving forward.

In contrast, Camron Dowlatshahi of Mills Sadat Dowlat LLP says TS has no legal standing in this matter -- but the one thing she's got is a whole lotta $$$ to bury JS in legal fees -- so, bottom line, he should probably watch his back.

Bottom line ... more people seem to think Jack's A-OK to keep tracking ... ball's in his court.