The following response does not constitute legal advice and your father should seek legal advice. Suspension is supposed to be a neutral act...often pending an investigation and...an employer may suspend someone..if it is a reasonable course of action...and it should really be on full pay...unless there is substantive evidence of gross misconduct.
Anyone can be escorted off private premises at the wish of the owners. While, your father has a contract ..of employment..presumably.. with the security firm he has no contract with the courts.
Therefore, if the court's contract with the security firm is nearing an end they are free.. and probably compelled..to put the contract out to tender on the open market and may chose another company to provide the security service. This would be fairly routine and should not involve your father being suspended. It may, however, make him redundant if there is no other security work available. However, whoever sanctioned the action must believe that they have a reason for doing so, and your father may have not told you the full story since parents often do not wish to burden their children with problems at work. Furthermore, your father should comply with the request not to discuss it with anyone at work since, if alerted to it, the court could argue that it was a breach of contract. It might also make resolution of the problem more difficult...hence the need for confidentiality. It is not unheard of for some employers to construct dismissals to avoid paying out redundancy payments and 10 years service would be a substantial sum. However, we have got to be careful about speculation.
End of part 1
Jock