I also have a 4-year-old MBP with a matte display (I'm so glad that back then, I decided to pay extra for that! Matte displays aren't even an option anymore for new MacBooks, are they?) and I find I can also work sitting in the sun. It really depends on the time of day/angle the light is hitting from/intensity of the sunlight. Wearing a cap with a peak/a visor/similar (it's all about shading the eyes) & turning the brightness of the screen up also helps.
To the OP: if you want to combine work and being outside and have everything that's necessary - basically a laptop which won't immediately overheat and whose battery is still doing alright (+ a WIFI stick if you need internet[1]) - go for it! If you don't have a matte display, look into privacy filters/screens (the one I have is shiny on one side and matte on the other), though those obviously work best on screens with a good backlight, even more so in sunglight.
If you do end up working outside, don't forget to use sunscreen and to stay hydrated!
[1]Alternatively, search for cafés with free WIFI that have outdoor seating or turn your phone into a WIFI hotspot (beware of mobile data costs though).
Hmm! I was originally going to say I've never heard of companies having codes of conduct, but I guess that's more because I'd have heard of them as internal "policies" or similar.