Jeff Bezos, founder and CEO of Amazon, pictured on Oct. 2, 2019. Elif Ozturk | Anadolu Agency | Getty Images

As big tech companies are grappling with how to handle political ads on their platforms, Amazon is part of the club. The company's policies for how it handles sponsored ads, or ads that boost product or brand listings, remain unclear in terms of how they're being interpreted and enforced. On one hand, Amazon says it bans ads for products related to campaigns or to promote politicians. But the site still has many examples of sponsored products promoting candidates' 2020 campaigns or political parties. There's also at least one example of an advertiser whose sponsored ad was removed by Amazon because it contained a reference to a political figure, which Amazon claims was a mistake. Amazon's current policy for sponsored products states that "Content related to campaigns, elections, or political issues of public debate; that advocates for or against a politician or a political party; or that personally attacks a political figure" is prohibited. But in a few quick searches CNBC found dozens of examples of sponsored products that appeared to flout these rules, including a "Michael Bloomberg 2020 President Supporter T-Shirt," a "Talk Bernie to Me Sanders 2020" T-shirt and one shirt reading "Trump 2020 The Sequel Make Liberals Cry Again." "We require that all advertisers comply with Amazon Advertising policies," an Amazon spokesperson told CNBC in an emailed statement. "We monitor ads for policy compliance using automated tools and review teams, and take action when those policies are not followed." Big tech companies' treatment of political advertising has come under scrutiny in recent months. Spotify recently announced it was suspending political ads for 2020, citing insufficient tools to vet the ads. Twitter announced in October that it would ban political ads entirely. Facebook has taken the opposite approach, refusing to remove or fact-check ads from candidates even when they contain false information. Meanwhile, Snap has said it fact-checks political ads that appear on Snapchat.

A sponsored listing for a "Liberals Suck" T-Shirt on Amazon. Megan Graham

Steve Yates, CEO of Prime Guidance, consults some third-party sellers that offer political-themed merchandise on Amazon. He said he continues to see "hundreds" of ads for political merchandise on the platform, and they often appear as the top result in search queries. Among the sponsored items he's seen include Donald Trump and Joe Biden apparel, he said. It shows that Amazon isn't preventing sellers from using political figures or names "as keywords to bid on," Yates added. "However, they are expecting sellers to self-police themselves by not engaging ads on the site targeting those keywords," Yates said. Yates said he advises any sellers he works with to follow Amazon's policies, even though it's apparent that other sellers do not. When consumers search for a product on Amazon, they're likely to notice products with a "sponsored" label. These are "sponsored products," or keyword-targeted ads that let advertisers promote certain products. To the untrained eye, it can be hard to tell they're ads at all. Here, advertisers bid on particular terms, and ads with higher bids are more likely to be displayed. Advertisers pay only when their ad is clicked, and they set the maximum amount they're willing to pay. This is similar to how search ads work on Google. These ads can appear above, near or within search results, or even on product detail pages.

Sponsored products for searchers looking for Elizabeth Warren products. Megan Graham

Amazon claims it mistakenly flagged novelty Trump apparel

But even as many political ads have slipped through unnoticed by Amazon, Amazon said other sponsored politically themed products that follow Amazon's policies have been mistakenly removed. In late December, Amazon told one agency that advertises on behalf of the maker of novelty Trump apparel that it could not place ads for a product because they contained a reference to a political figure. The message came from an Amazon support email sent to the agency that was viewed by CNBC. (The agency asked CNBC not to identify the product because they don't have the rights to disclose their client's brand.) In the email, Amazon said that per its advertising guidelines, "products with reference to any political figure and products that mock a person's appearance," are prohibited from advertising. The company said that "as of now these products are only eligible to sell on Amazon, however, advertising them on Amazon is prohibited." Amazon's email to the agency also said that "similar ads" may be found but to "please know that these ads were approved prior to the change in the advertising guidelines and our internal team is reviewing these ads on the website and suspending such ads from advertisement. Since there are so many ads in our website, they are taking some time to remove all the ineligible ads from Advertising." An Amazon spokeswoman said Monday, "The email that CNBC viewed contains inaccurate information and our long standing policies have not changed." The company said the product is actually permitted and that it was addressing the issue. But after the advertiser followed up later on Monday, Amazon sent them another email claiming the sponsored product was still in violation because the product was "related to a political figure." Will Tjernlund of Goat Consulting, an Amazon consulting agency who was working to place the ads on Amazon, said he understood why Amazon would be making a policy change, but said he wishes the company would do a better job of fully policing the policy. Amazon has had issues enforcing its ad policies in the past. In May 2019, the company told some small sellers it would no longer allow ads with religious content. Amazon later said that directive was a mistake, using identical language they used to comment on the politically related email this week, and said its employees would be retrained. But the sudden ad suspension in 2019 still took a direct hit on some sellers' sales. Both incidents are just the latest examples of Amazon's ongoing issues with the third-party marketplace, which now accounts for over half of the company's e-commerce volume. As the platform has grown to amass millions of sellers, it has become a hotbed for counterfeit, unsafe and expired goods, while the Amazon's Choice badge has also been called into question over reports it recommends fake, defective and inferior products. In response, legislators have written letters to CEO Jeff Bezos that call for the company to take steps to curb counterfeit goods and ask for more information about its product recommendation engine.