We have a problem with nut grass. (My mother bought dirt from a nursery and it was in the dirt) We pull it and its back in back in a week. She has used Roundup and it doesnt work. She bought a " nutgrass killer selective herbicide" by a company called Monterey this also had no effect. As you can see from pics below.
About 15 years ago, I had the same problem from a dirt yard. They also claimed no responsibility. I tried all of the above and nothing got rid of it. In the "off" season, I dug up the whole bed about a foot deep when it was soft and sifted all the stupid dirt and re-planted my dormant plants. It was back breaking work, but I was so mad it made it a little easier! The sifting got rid of the nuts and the roots (and many other weeds) so my bed was finally free of it. The down side was that it stirred up other dormant seeds that took a season or two to get rid of, but in the long run, it was worth it! Good luck!
I can tell you what doesn't work...I have it around my rose garden. News paper and mulch does not work. I saw it on Pintrest and tried it. Weeds still came through, especially the nut grass. I tried the weed killer designed for it and was not impressed. I think I may let it grow then just keep it trimmed...you know, if you can' t beat it...etc IF anyone has a suggestion that would work I'd appreciate hearing the miracle cure for nut grass.
I do landscaping and have had some success using the chemical "Image". It is somewhat selective, but must be used while the nut grass is actively growing before the leaves harden off. It is absorbed better through new growth and sometimes takes 2 treatments. Pulling has little effect unless you are extremely vigilant and roundup only kills the top. Comes back quickly from the nut.
I also had this "turn up" last year in my back garden. Is there really a "nut" that this grows from? What does it look like? I weeded and weeded last year and saw nothing but roots. I don't know where it came from, but I'm blaming my husband as he has horses and I think it must have been in some hay or straw! The pasture is upwind from the back garden and I'm always getting odd weeds because the wind blows the seeds down into the garden.