Google Quality Guidelines: Link Schemes Update on October 26, 2018

Last week. Google updated their Link Schemes guidelines for the first time in a while. This update has to do with links generated as a result from a contract or agreement.
Specifically, Google added one line to its link schemes forbidding:

Requiring a link as part of a Terms of Service, contract, or similar arrangement without allowing a third-party content owner the choice of using nofollow or other method of blocking PageRank, should they wish.

Links generated in this fashion could negatively affect a site's rankings.

When would contractual links like this occur? 

I can think of several examples:

• If a web dev or marketing company requires its clients to include a link to their site, as a site credit for example.
• If a web host includes a link that cannot be removed per their TOS, as a lot of free web hosts have.
• If a TOS for a widget or embedded tool requires a link to their site.

(If you can think of any other circumstances where a link might be required, please include them in the comments, below)

What you should do about contractually obligated links? 

According to this new guideline, you should make sure the link doesn't pass PageRank by nofollowing the link. I believe it's important to note that this might not only affect websites receiving these links. Google holds sites accountable for those to whom they link to, as well. If your site includes a link like this, you should remedy this link by nofollowing it (or even removing it altogether. 

While doing backlink research for some clients, I've noticed footer links returning in fashion. For a while, companies would remove these from their clients' sites. Now more and more web dev and marketing companies are including them. I wonder if this guidelines change is a response to this move. 

A change to Google's Link Schemes guidelines is rare. Over the last couple of years Google has simply been ignoring bad links to a site. By adding this restriction on contractually-obligated links, Google is explicitly stating that these links are not only a violation of their rules but something that would adversely affect sites. I'd suspect that in the next couple of months some webmasters will receive notifications for links like this- and possibly penalties. Check your messages in Google Search Console (or the Manual Action tab in Google's old Webmaster Tools interface) for these, if you've been doing this.