they have a right to choose who to employ, unless u can prove discrimination

A company is not required to interview anyone, and they are not entitled to give a reason.

My suggestion is use your work experience from that company to get a better job.

Yes, it is legal to deny an interview. They already know they are not going to hire you so there is no reason to waste your time and theirs.

There is no law that indicates that they need to interview you, ever. They are required to accept your application for employment if they have a position open. They are required not to discriminate based on race, religion, gender, etc. They are, however, legally able to discriminate on the basis of one old manager who doesn’t like you for personal reasons. If they perform interviews (which are not legally required as a basis for employment) they would only interview likely candidates and it doesn’t look like you are one, in their eyes.

I see you’ve already got the good old American sense of over-entitlement.
Any company can interview (or not interview) anyone they choose. Even if your old manager doesn’t like you that isn’t illegal.

Yes it is legal. They can decide not to interview for any reason including “I just don’t feel like it”. There may be many reasons for them not interviewing you and the top reason is probably because they don’t want to deal with any immigration issues that may come up for you. Another reason could be that there were others who applied for that job that had more to bring to the company.

It is not the role of government to interfere in the daily goings on in business, and to legistlate what’s fair and what’s not.

Move on to another company, or better yet, start a small one of your own.