I am in a long distance relationship with my boyfriend who lives in Slovakia. I just got back from a 3 month trip in Europe (I'm an U.S citizen,) and my boyfriend who resides in Slovakia (non U.S. citizen) wants to come to the U.S for one week in March. He has an ESTA visa. The problem is, we are afraid to have him come in March because he plans on coming in June as well and staying for 90 days. This would be his 3rd year in a row traveling to the U.S in June for 90 days. 1st year was J1 visa. Second year was tourist (ESTA) and this being the third year. We're afraid that if he takes the trip in March that they could deny him in June. What to do! Advice?!?
A foreigner entering the US (especially a visitor) can always be denied entry. There is nothing inherently problematic with his pattern of travel. It is very reasonable to have visited the US for a few days, and then after a space of a few months later to visit again. People visit more frequently than that with no problem. It's not like he's trying to do a visa run (stay for almost the 90 days, leave for a few days, and then come again).
A bigger potential source for problems, in my opinion, is the fact that he is coming to the US to visit his US-citizen significant other. It's so easy for you guys to decide to get married on a whim, after which he can stay, so that poses immigrant intent issues.
The official rules are clear as mud:
When traveling to the U.S. with the approved ESTA, you may only stay for up to 90 days at a time - and there should be a reasonable amount of time between visits so that the CBP Officer does not think you are trying to live here. There is no set requirement for how long you must wait between visits.
If he is not trying to live in the United States, and can actually show evidence that he will return to his home country at the end of the visit, then he should be fine. Such evidence might be something like a university admission, or documentation of anything else that would require his presence outside the US.