Per Northwoods League website
"To play in the Northwoods League an individual must be a current college baseball player or a recently graduated pitcher and should have aspirations of playing professional baseball."
https://northwoodsleague.com/apply/
I do not know about every kid but the ones I know that entered the portal were told they would not be allowed to play in their Summer League through the Coastal Plains League because they were considered not enrolled and not a current college baseball player as it say in Northwoods League. That is also what the owner told me this week. He had a few that he had to contact and tell they could not come as long as they were in the portal unless they got a commitment and enrolled in another school which fit into their league's level of play. They only take kids from certain levels of play. I just stated what I was told by players and a league team owner. I also texted a guy in administration with a Cape Cod League team and he said that is their rule also but it rarely comes into play for their guys.
My original statement was most of the upper leagues of college ball. Don't shoot the messenger.