The Supreme Court justice was all smiles Friday morning in D.C. as she walked gingerly to her car ... presumably heading off to the office. It's a safe bet she didn't stop to sip on some fine Napa Valley red for a BD celebration. But then again, who knows ... RBG's badass!

Great to see RBG back on her feet. As we showed you ... Ginsburg walked slowly but steadily last month as she landed at Reagan National Airport, still recovering from her recent cancer surgery. She was flanked on all sides by security who kept a watchful eye on her.

The SCOTUS icon is fully back in action, after missing a few weeks in the wake of her latest health scare.