Far too extreme for a newbie. Not every newbie is a bot and looking to share shady and scammy links. Some newbies are genuine and looking to grow with the community as they learn and if you impose such it simply means new members are not welcome.
How will a newbie able to post from an external source if they not able to share a link of my source? won't it earn them an automatic ban for "plagiarism''?

Sometimes a newbie may need to ask for Help/support with reference to Links or Some other Newbie may be willing to help with reference using a link but can not do so because they can't post links. Now how does that help the community to grow?
Much as we need to get rid of Newbie bots, we should also consider that there are genuine newbies.