Shabbos and Kosher

I recieved the following question:
I understand that you give the kosher supervision for (Certain Restaurant) in Manhattan. How is it possible for it to be kosher when it is open on the Sabbath?

Thanks for answering!

And I answered the following:
Hello,
Thanks for the question.
According to Jewish Law, Shabbos and Kosher are two different things. Being open on Shabbos does not effect the Kosher status of the food.
Of course we want every Jew to be all that they can be and keep the Shabbos as holy as can be. BUT if someone does not keep Shabbos it does NOT at all mean that their Kosher standards are compromised.
Unfortunately, in this world of convoluted and unnecessary stringencies we are made to believe the opposite, that Shabbos is somehow a Kosher standard.
When I was young, reliable certifying agencies did give certification to restaurants and businesses open on Shabbos. And even now all the major certifying agencies (OU, OK, etc.) certify factories that produce on Shabbos.
If I can help you any more please feel free to contact me further.
Have a good Shabbos.
Rabbi Schwarcz