That happened some time ago. And it is not unusual for the politicians to do that. Keeping your law license alive in the modern world in not an easy task--in one of the states where I am admitted, it takes two separate filings every year in two separate envelopes each containing five or six sheets of paper most of which are manually executed.
You need to do 15 hours a year of CLE--you can't always get credit in one jurisdiction for CLE you did for another.
So then the politician like Obama looks at what revenue he might ever recognize from his law license and realizes that it is not essential to much of anything he might ever do--in the present law environment, his value to a firm is the business contacts would bring to the firm; which is the value he was banking in his law firm relationship before he was first elected.
What really counts for use of the license is going down to the courthouse and making an appearance before a judge; or being the lawyer up front making the decision about the advice to be given to a client; signing an opinion as to the legal consequences.
Obama never did much of that stuff and he really wasn't qualified to do so. He was an affirmative action lawyer with contacts that brought business to the firm which competent lawyers at the firm could do the real legal work to service and charge enough for to get income to Obama.
NOTE
Can’t disbar him. He’s not registered to practice. https://www.iardc.org/ldetail.asp?id=911307036
NOTE
Can’t disbar him. He’s not registered to practice. https://www.iardc.org/ldetail.asp?id=911307036