Is it legal to use paracord to block other robots?
no, the only rope availbe to use in VRC is 1/8th inch braided nylon rope
First, any question about “it is legal” almost always has it’s answer in the game manual, here’s where you can get one: https://content.vexrobotics.com/docs/vrc-tower-takeover/GameManual-20190816.pdf
Next, paracord is usually 1/8" nylon rope, so take a look at rule R7 (e) on page 25. Next, review rule G12 on page 17 (along with the rest of the rules in the game manual), and decide if your intended use of the paracord would be legal according to the game manual.
If you still have a question or concern about a rule, then perhaps re-post what rule you are looking at…
which sometimes is sold as Paracord. I put in a Q&A about paracord for this season and its long as it is 1/8" braided nylon, you are ok.