I live behind a liquor store who started with an umbrella, table and chairs next to his building and has now did the same toward the curb. This is in addition to a sign for passing cars advertising his store. He is copying several other businesses on this block doing the same thing. A coffee shop set up so much stuff that with the bus stop bench there, you practically have to walk on the street to get by.
Food sellers and other retailers must have permits for sidewalk seating and/or serving, and the space and number of seats and tables is strictly limited. Contact your local police department or the staff-person for constituent services in your City Council district and ask that the retailer's encroachment be compared with the authorization on file for that use by that address. If the retailer's use of sidewalk space is within the allowed authorization, ask your city council district office to consider whether the authorization needs to be scaled back.