It is not illegal for the mailman to hand you your mail.
Although it can be against the policy for the mailman to hand you your mail, but it's not illegal.
And while it might be against post office policies for the mailman to hand you your mail, they often still do so, especially if they know you and have been delivering mail to you a lot.
It's also often considered to be a common courtesy for a mailman or postal carrier to hand you your mail, when you're present.
It's also a standard part of the mail delivery process, as mail carriers are also required to deliver mail to your address unless there are operational issues or safety concerns.
Most mailman and mail carriers will gladly hand you your mail directly, especially if it's a package or if you're at the door when they arrive to deliver the mail.
Although a mail carrier might not hand you your mail if your mailbox is full of unauthorized items or if there are safety concerns or they are unsure if it's the actual person that is supposed to get the mail.
My mail carrier hands me my mail when I see him and it's never been an issue, but it can vary depending on the mailman.
If the mail carrier is not able to hand you, your mail or is reluctant to, then they can and will just place the mail into your mailbox or leave a package at your door, or if they can't, the mail carrier will leave a note to pick up the package or other mail at the post office.