A self-represented party is required to identify themselves that way on court papers. If you ever look at a probate petition filed on pleading paper, the petition will list in the upper left-hand corner of the 1st page the attorney's name and their bar number, e.g. 258625 (my bar number). For a self-represented party, they will write "pro per" or something similar to that near their name.
Self-representation is permissible because a third-party is not involved. Attorney licensing is required, so the theory goes, to protect clients from unlicensed attorneys who might cause them irreparable harm through incompetent representation. However, there is nothing that prevents a party from representing themselves in an action. Attorney licensure requirements do not protect a party from themselves.
An associated issue that comes up with self-represented parties is whether they are entitled to attorney fees. Normally attorney fees are not awarded to even the prevailing party, much less the losing side. Each side bears their own cost of litigation. The exceptions for this rule, in the probate context, involve certain causes of action. For instance, attorney fees are recoverable under the common fund theory for a beneficiary. See Copley v Copley (1981) 126 CA3d 248, 292. Still, attorney fees are not recoverable for a self-represented party, even if the party is an attorney. See Musaelian v. Adams (2009) 45 Cal.4th 512, 520. So even if a self-represented party prevails in a probate matter and spent 50 hours working on the case, they will not be compensated for the time they spent on the matter.
Logically it makes sense to bar a self-represented party from recovering attorney fees, even if they are an attorney. The prohibition recognizes that attorney fees are for a third-party, not the party themselves. Allowing attorney fees for a self-represented party would create the impression that the self-represented party is somehow two people, the client and the attorney. That would be a neat trick, but such obviously defies reality.
Moreover, since nearly all self-represented parties are not attorneys, the prohibition ensures that there is no attorney licensure loophole. One would expect that attorney fees are reserved for attorneys. If you are not an attorney, you do not receive them.
