You have the ability to limit what teams players are able to select when registering within a program.
Click on the blue "Club" tab located at the top of the page and then click "Programs" located in the black menu bar. Once under programs, click on "Program Registrations" located in the grey menu bar. When viewing program registrations, use the filters to view the registrations for the specific program.
Once in program registrations select "Show" in the "Team Column" dropdown. All the available teams will line up on the right of the list of players in the program.
To remove a team from the program, click on the X in the top right of the team box.