Can my husband's company prohibit me from staying in his hotel room on a business trip?

My husband is employed in California with a global corporation, and will be traveling to Illinois for a 10-day company training. The company will be paying for individual hotel rooms at a single hotel for the attendees. There are set training hours for each day, and training takes place at a company location away from the hotel. There are no scheduled "after hours" employee events. The company is prohibiting me and our child from staying with my husband at the hotel. We are planning to join him in Illinois (flying there, separately from him, on our own dime and paying all of our own expenses while there) so this is not a business expense issue. The company claims that "for the purposes of this training the hotel is considered (company name) property," and company policy states that employees may not have friends or family visit or stay with them in hotel rooms. Is this a violation of California's employee right to engage in lawful off-duty conduct? Is this a violation of a California employee's right to reasonable privacy? Can the company claim the hotel serves as "company property" during the training? Does California or Illinois law apply here? Thank you in advance!