Although it may not be illegal to include competitor's registered trademarks in your Metatag list, it is likely to give rise to a potential lawsuit and claims for damages.
Metatags are used by search engines to identify key words and phrases which help to drive traffic to your website. It may be tempting to include the names of all of your competitors so that anyone searching for their company also gets your business in the listings. This is a very bad plan! Any traffic which comes to your site as a result of this opens your company up to a claim for damages - you wouldn't include their name in a printed advertisement.
So, these things are hidden in the code of the website, who would ever know? It is very easy to check a web page's source code (most browsers allow you to do this) and there is all of the metatag data.
But if these tags are entered by the administrator of the website in my company, is that my responsibility? Very much so is the likely answer. The directors or partners are responsible for the company.
I sell products made by other people, can I use their trademark's in the metatags? The answer seems to be yes, providing it is to sell their products and you are legitimately selling those products.
The rules for these types of infringements are determined by the courts. Generally speaking, it is usually best not to put yourself in the position of having to defend a potentially damaging situation.
If you would like help to check what hidden things your website is saying, please contact cleartarn. At no cost to you we will happily show you how to access the data. It is very likely that you will know immediately whether it is likely to cause you a problem.
At the same time you might want to explore how you can really raise your company up your search engine rankings by taking a look at Search Engine Optimisation on the cleartarn website.