I'm not sure what the claim or charge would be. While I wouldn't feel comfortable participating in political campaigns for democracies of other countries, and I would feel defensive about attempts to influence elections in my country, in the end these 'attacks' rely on actual citizens to vote, so the citizen still holds the power and makes the final decision, so I don't think it's an issue of critical severity, and I don't think it's illegitimate to try to persuade citizens of another country to vote in such matter at a constitutional level (excluding specific laws), even if I personally would feel icky about it.
Now there may be other potential issues that would elevate the matter, if disinformation is used, or if personal information about citizens is obtained illegitimately, then they could constitute crimes in their own right. Whether the crime is aggravated by its intent to subvert the democratic institution would be a legitimate question, but without the accessory crimes, I don't think political campaigns from non citizen actors are themselves illegal, just icky.
Now there may be other potential issues that would elevate the matter, if disinformation is used, or if personal information about citizens is obtained illegitimately, then they could constitute crimes in their own right. Whether the crime is aggravated by its intent to subvert the democratic institution would be a legitimate question, but without the accessory crimes, I don't think political campaigns from non citizen actors are themselves illegal, just icky.